Method for polishing surgical stents

ABSTRACT

A method for polishing radially expandable surgical stents is disclosed where fluid abrasive media M flows over surfaces of the stent  10  causing the surfaces of the stent  10  to be polished and streamlined. The stent  10  is temporarily provided with cylindrical support ends  20,  which are not radially expandable to support the stent  10  during the polishing process. An interior polishing fixture  100  is provided which has cylindrical chambers  135  therein adapted to receive a stent  10  therein. Fluid abrasive media M then flows into bores  108  in the fixture  100  leading to the cylindrical chambers  135  and adjacent the inner diameter surfaces of the stent  10.  Surfaces of the stent  10  forming the outer diameter are polished by placing the stent  10  within an exterior polishing fixture  200  which has a cylindrical recess  220  therein. The cylindrical recess  220  has a diameter greater than a diameter of outer surfaces of the stent  10  and includes a cylindrical shaft  270  passing axially through the cylindrical recess  220  upon which the stent  10  is located. Slanted bores  208  pass through walls of the exterior polishing fixture  200  and into the cylindrical recess  220,  directing the abrasive media M adjacent exterior surfaces of the stent  10  and causing polishing of the exterior surfaces of the stent  10.  The direction of abrasive media M flow can be reversed to make streamlining of segments of the stent  10  occur in a symmetrical fashion. After polishing of the stent  10  is completed, the cylindrical support ends  20  are removed and the stent  10  is ready for implantation and radial expansion within a body lumen L. When polished and streamlined, the radially expandable surgical stent  10  more effectively supports a body lumen L without excessive thrombus, restenosis and other medical complications.

“This is a continuation of U.S. patent application Ser. No. 08/870,962filed Jun. 6, 1997 now U.S. Pat. No. 5,746,691.”

FIELD OF THE INVENTION

The following invention relates to the polishing of radially expandablesurgical stents which can be surgically implanted into a body lumen,such as an artery, and be radially expanded to support the lumen. Morespecifically, this invention relates to fixtures used for supporting aradially expandable surgical stent while an abrasive media is flowedover surfaces of the stent to polish the stent and provide an innersurface of the stent with a streamlined contour, and methods for usingsuch fixtures while polishing surgical stents.

BACKGROUND OF THE INVENTION

Surgical stents have long been known which can be surgically implantedinto a body lumen, such as an artery, to reinforce, support, repair orotherwise enhance the performance of the lumen. For instance, incardiovascular surgery it is often desirable to place a stent in thecoronary artery at a location where the artery is damaged or issusceptible to collapse. The stent, once in place, reinforces thatportion of the artery allowing normal blood flow to occur through theartery. One form of stent which is particularly desirable forimplantation in arteries and other body lumens is a tubular stent whichis formed as a complete tubular cylinder and can be radially expandedfrom a first smaller diameter to a second larger diameter. Such radiallyexpandable stents can be inserted into the artery by being located on acatheter and fed internally through the arterial pathways of the patientuntil the unexpanded stent is located where desired. The catheter isfitted with a balloon or other expansion mechanism which exerts a radialpressure outward on the stent, causing the stent to expand radially to alarger diameter. Such expandable stents exhibit sufficient rigidityafter being expanded that they will remain expanded after the catheterhas been removed.

Radially expandable stents come in a variety of different configurationsto provide optimal performance in various different particularcircumstances. For instance, the patents to Lau (U.S. Pat. Nos.5,514,154, 5,421,955, and 5,242,399), Baracci (U.S. Pat. No. 5,531,741),Gaterud (U.S. Pat. No. 5,522,882), Gianturco (U.S. Pat. Nos. 5,507,771and 5,314,444), Termin (U.S. Pat. No. 5,496,277), Lane (U.S. Pat. No.5,494,029), Maeda (U.S. Pat. No. 5,507,767), Marin (U.S. Pat. No.5,443,477), Khosravi (U.S. Pat. No. 5,441,515), Jessen (U.S. Pat. No.5,425,739), Hickle (U.S. Pat. No. 5,139,480), Schatz (U.S. Pat. No.5,195,984), Fordenbacher (U.S. Pat. No. 5,549,662) and Wiktor (U.S. Pat.No. 5,133,732), each include some form of radially expandable stent forimplantation into a body lumen.

Some problems which have been exhibited by prior art stents include thatthe inner and outer surfaces of the stents are not sufficientlystreamlined or finely enough polished to prevent certain medicalcomplications. For instance, thrombus, a phenomenon where a fibrous clotforms within cracks and other irregularities in the surface finish of animplanted object (such as a stent), is enhanced when the surfaces of thestent are not finely polished. Additionally, when the inner surface ofthe stent is substantially planar and has abrupt edges along bordersthereof, turbulence is introduced into the blood. When a stent havingsuch an abrupt edge is implanted into an artery, plaque and otherdeposits are provided with a site for collection and potential narrowingof the arteries and restriction of blood flow. This plaque buildupadjacent an implanted object (such as a stent) is referred to as“restenosis.”

While many prior art stents do exhibit somewhat polished surfaces, theyare typically not sufficiently finely polished, especially on tubularstents having smaller diameters, to prevent restenosis and thrombusadjacent the stent after the stent is implanted into the artery. Suchprior art stents also lack a streamlined contour to minimize disruptionof bodily fluid flow through the lumen and to further discouragerestenosis surrounding the stent.

A primary reason why prior art stents fail to exhibit sufficientlyfinely polished surfaces to avoid the drawbacks discussed above is thelack of a polishing process which can effectively provide the finelypolished surface desired, especially on stents having smaller innerdiameters. Stents are typically polished in one of two processes, eitherchemical etching or electropolishing. With chemical etching, chemicalsare used which react chemically with the material forming the stent,causing the material forming the stent to be driven into solution.Chemicals are selected which have a strength sufficient to cause roughareas of the stent to be dissolved, but not so strong that smooth areasof the stent are detrimentally altered. Chemical etching, while somewhateffective in removing gross irregularities from the surfaces of thestent, fail to adequately provide the desired finely polished surface.

Electropolishing typically involves providing an electrolytic solution,placing the stent within the electrolytic solution, placing a cathodewithin the solution and not contacting the stent and coupling an anodeto the stent. When an electric voltage is provided between the anode andthe cathode, the stent is caused to lose portions of its outer surfacewhen the elements forming the stent are driven into solution and carriedto the cathode for deposition upon the cathode. In essence, suchelectrolytic polishing is the reverse of commonly used electricalplating processes with material from the surface of the stent beingremoved rather than added to the stent. The rougher surfaces of thestent are more readily driven into solution and hence removed from thesurfaces of the stent, smoothing the surfaces of the stent somewhat.

Because the surfaces of the stent forming the inner diameter of thestent benefit from a high degree of polishing, one known technique is toform the cathode as a thin wire passing along a central axis of thestent entirely through the stent from one end to the other, but withoutphysically contacting the stent. When a voltage is provided between thecathode wire passing along the central axis of the stent and the stentitself, the inner surfaces of the stent are provided with the greatestelectric field density and hence are the surfaces which are mostpolished during this process. While typically more effective thanchemical etching, electrolytic polishing also fails to provide asufficiently finely polished stent to significantly discourage thrombusand restenosis adjacent surfaces of the stent.

Accordingly, a need exists for a method and apparatus for polishingsurfaces of a radially expandable surgical stent, and particularly thesurfaces forming the inner diameter of the stent, with a sufficientdegree of polish to reduce or eliminate the occurrence of thrombus andrestenosis when surgical stents are implanted within a body lumen.

SUMMARY OF THE INVENTION

The radially expandable surgical stent which is polished and streamlinedby the method and apparatus of this invention exhibits an overalltubular cylindrical hollow seamless contour which can feature any of avariety of different arrangements for individual elements and segmentsforming the stent. The various different segments of the stent have agenerally elongate, substantially constant cross-sectional contour whichcan either be oriented to extend axially, circumferentially, or somecombination thereof, with each segment located between an inner diameterof the stent and an outer diameter of the stent. Each segment includesan outer surface coextensive with the outer diameter of the stent and aninner surface coextensive with the inner diameter of the stent. Eachsegment also includes lateral surfaces extending between the innersurface and the outer surface which can either be a leading surface onan upstream side of the segment, a trailing surface on a downstream sideof the segment, or a lateral surface generally aligned axially with thestent.

The inner surface of each segment of the stent is extensivelystreamlined by the polishing method and apparatus of this invention tominimize disruption of bodily fluid flow through the body lumen.Specifically, the inner surface includes an inner leading edge and aninner trailing edge bordering the inner surface. Each inner edge isdefined by an inner curve having a relatively large radius of curvaturewhen compared to the radii of curvature exhibited by outer edgesadjacent the outer surface of each stent segment. Because the inneredges have a large radius of curvature, they do not present any abrupttransition in flow for bodily fluids passing over the inner surface ofthe stent segment, particularly when the stent segment is alignedcircumferentially with bodily fluid flow passing adjacent the innersurface from a leading inner edge to a trailing inner edge.

The surfaces of each stent segment are honed and polished to have asurface finish which is free from abrupt transitions and irregularities,such as prominences extending more than five micro inches above adjacentportions of the surrounding surface. Smooth flow of blood or otherbodily fluids over the surfaces of the stent can thus be preserved and arisk of medical complications such as restenosis and thrombus can beminimized.

The polishing apparatus of this invention includes a fixture whichrigidly supports at least one radially expandable surgical stent withina cylindrical chamber in the fixture. A bore passes through the fixtureand leads both into the cylindrical chamber and out of the cylindricalchamber. A source of fluid abrasive media is placed adjacent the fixturein an orientation which allows the fluid abrasive media to pass throughthe bores and into the cylindrical chamber. The cylindrical chamber hasa diameter similar to the outer diameter of the stent so that the fluidabrasive media is forced to pass only through the interior of the stentand adjacent the surfaces forming the inner diameter of the stent. Asthe fluid abrasive media passes through the cylindrical chamber andadjacent the surfaces forming the inner diameter of the stent, thesurfaces forming the inner diameter of the stent are polished to a levelof smoothness determined by the particle size of the abrasive media, theamount of time which the abrasive media flows past the surfaces of thestent and other factors known in the honing arts.

When it is desired that the outer diameter of the stent be polished, astent exterior polishing fixture is provided having a cylindrical recesslocated therein with slanted bores leading from a top and bottom of thefixture to the cylindrical recess. The cylindrical recess has a diametergreater than the diameter of the outer diameter of the stent. A shaft islocated within the cylindrical recess with a central axis of the shaftaligned with a central axis of the cylindrical recess. The shaft has adiameter similar to the inner diameter of the stent. The stent is placedon the shaft and within the cylindrical recess so that abrasive mediaflowing through the slanted bores and into the cylindrical recess areprecluded from flowing adjacent the surfaces forming the inner diameterof the stent, but rather flow adjacent surfaces forming the outerdiameter of the stent for polishing of the outer diameter of the stent.

In utilizing the various fixtures for supporting the stent during thispolishing process, the stent is preferably initially provided with,radially-non-expandable cylindrical support ends adjacent each end ofthe stent. These cylindrical support ends are located along with thestent within the cylindrical chamber or cylindrical recess of one of thefixtures and provide additional support for the stent during thepolishing process. The support ends prevent collapse of the stent andexcessive polishing of ends of the stent during the polishing process.

The polishing process can be additionally facilitated by ultrasonicallyvibrating the abrasive media and elevating the pressure of the abrasivemedia as it flows through the fixture and adjacent surfaces of thestent. If it is desired that the stent be provided with a streamlinedcontour which is not biased in any one direction, the stent can beremoved and reoriented within the fixture for polishing in a reversedirection or the fixture can be disconnected from the source of abrasivemedia, rotated 180° and recoupled to the source of abrasive media forpolishing in a reverse direction. Once the polishing process iscompleted, the cylindrical support ends are removed from the stent. Thestent is then ready for implantation within a body lumen with suchfinely polished surfaces that restenosis and thrombus are minimized.

OBJECTS OF THE INVENTION

Accordingly, a primary object of the present invention is to provide amethod for polishing surfaces of a radially expandable surgical stentwhich includes flowing a fluid abrasive media adjacent surfaces of thestent to be polished until the stent exhibits a desired finish.

Another object of the present invention is to provide a method forstreamlining surfaces of a radially expandable surgical stent by flowingfluid abrasive media adjacent surfaces of the stent to be streamlined.

Another object of the present invention is to provide a method forpolishing a radially expandable surgical stent which can polish multiplestents simultaneously.

Another object of the present invention is to provide a fixture for aradially expandable surgical stent polishing process which holds andsupports the stent while fluid abrasive media is flowed adjacentsurfaces of the stent and which can be easily loaded and unloaded withstents to be polished.

Another object of the present invention is to provide a fixture for astent polishing process which restricts fluid abrasive media flow to thesurfaces forming the inner diameter of the stent.

Another object of the present invention is to provide a fixture for astent polishing process which restricts fluid abrasive media flow to thesurfaces forming the outer diameter of the stent.

Another object of the present invention is to provide a stent polishingfixture which can be readily attached to honing equipment which useselevated pressure fluid abrasive media and ultrasonic vibration of thefluid abrasive media and directs the fluid abrasive media through thefixture.

Another object of the present invention is to provide a surgical stentwhich minimizes medical complications such as restenosis and thrombusadjacent the stent.

Another object of the present invention is to provide a radiallyexpandable surgical stent which has a finish smoothness which minimizesmedical complications such as restenosis and thrombus adjacent the stentwhen the stent is implanted within an artery or other body lumen.

Another object of the present invention is to provide a surgical stentwhich can support a body lumen while minimizing disruption of flow ofbodily fluids through the lumen.

Another object of the present invention is to provide a surgical stentwhich is reversible and can be implanted in two distinct orientationsrotated 180° from each other without altering performance of thesurgical stent.

Another object of the present invention is to provide a surgical stentwhich features an inner surface which has edges with greater radii ofcurvature than radii of curvature of outer edges bordering an outersurface of segments of the stent, such that disruption to blood flowwithin a body lumen in which the stent is implanted is minimized and theouter surface of the stent is securely held adjacent a wall of thelumen.

Other further objects of the present invention will become apparent froma careful reading of the included description and claims and from areview of the drawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a radially expandable surgical stentwith cylindrical support ends located adjacent each end of the stent,such that the stent is ready to be placed within a fixture for polishingof surfaces of the stent. The stent is shown with circumferentialelements radially expanded to make surfaces of the stent more readilydiscernible. However, the circumferential elements of the stent would infact be not radially expanded when attached to the cylindrical supportends.

FIG. 2 is a cylindrical projection of a portion of that which is shownin FIG. 1 with the circumferential elements shown not radially expandedas the circumferential elements would appear when attached to thecylindrical support ends and during the polishing process of thisinvention.

FIG. 3 is a top plan view of a stent interior surface polishing fixturefor use according to the polishing method of this invention.

FIG. 4 is a full sectional view of that which is shown in FIG. 3 takenalong lines 4—4 of FIG. 3.

FIG. 5 is a perspective exploded parts view of that which is shown inFIG. 3 revealing how separate plates of the fixture are coupled togetherto form the fixture of FIG. 3.

FIG. 6 is a sectional view of the fixture of FIG. 3 with other portionsof the honing equipment and fluid abrasive media supply attached to thefixture and revealing how fluid abrasive media is caused to flow throughthe fixture and adjacent surfaces of the stent forming the innerdiameter of the stent.

FIG. 7 is a full sectional view taken along lines 7—7 of FIG. 8 andrevealing details of a polishing fixture for polishing exterior surfacesof a stent.

FIG. 8 is a top plan view of the stent exterior surface polishingfixture with interior details thereof shown with broken lines to showlocations of voids within the fixture.

FIG. 9 is a perspective exploded parts view of that which is shown inFIGS. 7 and 8 revealing how the stent is oriented within the stentexterior surface polishing fixture for polishing of exterior surfacesforming the outer diameter of the stent.

FIG. 10 is a perspective view of a portion of an alternative stentbefore any polishing of surfaces of the stent has occurred.

FIG. 11 is a perspective view of that which is shown in FIG. 10 afterpolishing of surfaces of the stent has been completed according to thisinvention.

FIG. 12 is a perspective view of a portion of that which is shown ineither the stent of FIG. 11 or the stent of FIGS. 1 and 2 revealing ingreater detail the exact streamlined contour of the segments of thestent after the polishing method of this invention has been completed.

FIG. 13 is a perspective view of a segment of a stent when only theportions of the stent forming the inner diameter of the stent have beenpolished and with surfaces forming the outer diameter of the stent leftunpolished.

FIG. 14 is a perspective view of a portion of that which is shown inFIG. 10 revealing how the surfaces of the stent exhibit roughness beforethe polishing method of this invention is performed.

FIG. 15 is a full sectional view of that which is shown in FIG. 12revealing further details of the streamlined contour of segments of thestent after completion of the polishing method according to thisinvention.

FIG. 16 is a full sectional view taken along lines 16—16 of FIG. 18 andshowing a body lumen with a stent, polished according to this invention,located within the body lumen and radially expanded within the bodylumen to support walls of the lumen.

FIG. 17 is a full sectional view of a body lumen with a non-polished orminimally polished radially expandable surgical stent located thereinand revealing turbulent blood flow, restenosis and thrombus within thebody lumen.

FIG. 18 is a full sectional perspective end view of the polishedradially expandable surgical stent in position within a body lumen andradially expanded therein.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings, wherein like reference numerals representlike parts throughout the various different drawing figures, referencenumeral 10 is directed to a radially expandable surgical stent (FIG. 1)which has been fitted with non-radially expandable cylindrical supportends 20 at each end of the stent 10. Surfaces of the stent 10 forming aninner diameter of the stent 10 are polished by placing the stent 10within a stent interior polishing fixture 100 (FIGS. 3-6) and flowingfluid abrasive media M through the fixture 100 with the stents 10therein. A stent exterior polishing fixture 200 (FIGS. 7-9) is alsoprovided which is configured to polish surfaces of the stent 10 formingan outer diameter of the stent 10 by flowing the abrasive media Madjacent the exterior surfaces of the stent 10. The abrasive media M notonly polishes surfaces of the stent 10 but also alters a cross-sectionalcontour of stent segments 40 (FIGS. 10-15) such that an inner surface 44is streamlined to minimize disruption of bodily fluid flow passing overthe inner surface 44 when the stent 10 is implanted within a body lumenL (FIGS. 16 and 18) after removal of the cylindrical support ends 20.The fixtures 100, 200 and other details of the polishing method of thisinvention can be altered to polish surfaces of the stent 10 in variousdifferent manners and also to alter a contour of surfaces of the stent10, such as to streamline surfaces of the stent 10, to cause surfacedetails of the stent 10 to match any of a variety of different desiredcontours and with a variety of different finish smoothness. However, apreferred contour for the stent 10 and stent segments 40 (FIG. 11) of analternative stent 30, having slightly differently configured stentsegments 40 than the circumferential elements 12 and axial elements 14of the stent 10 (FIGS. 1 and 2), is described in detail. By altering thepolishing methods discussed below, stents having different contourcharacteristics could similarly be generated.

In essence, and with particular reference to FIGS. 11 and 12, thecross-sectional contour of each stent segment 40 is described, whetherthe stent segment 40 is taken from the stent 10 or from the alternativestent 30. Each stent segment 40 is an elongate construct ofsubstantially constant cross-sectional generally rectangular form,having an outer surface 42 opposite an inner surface 44. Two lateralside surfaces including a leading surface 46 and a trailing surface 48extend between the inner surface 44 and the outer surface 42. The innersurface 44 is provided with an inner leading edge 54 and an innertrailing edge 56 which are defined by an inner leading curve 60 and aninner trailing curve 62, respectively, with sufficiently high radii ofcurvature 70, 72 (FIG. 15) that the inner surface 44 is highlystreamlined between the inner leading edge 54 and the inner trailingedge 56.

The outer surface 42 extends between two side edges including an outerleading edge 50 and an outer trailing edge 52. The outer leading edge 50is defined by an outer leading curve 64 and the outer trailing edge 52is defined by an outer trailing curve 66. The outer leading curve 64 andouter trailing curve 66 have radii of curvature 74, 76 (FIG. 15) whichare less than the radii of curvature 70, 72 of the inner leading curve60 and the inner trailing curve 62 (FIG. 12). The stent segment 40 thushas a contour which presents a highly streamlined gradually curvingsurface for passage of bodily fluid B (FIG. 16) there over and the outersurface 42 presents a more abrupt contour for secure positioningadjacent an inner surface S of the body lumen L (FIGS. 16 and 18).

Before polishing, the stent segments 40′ (FIG. 14) of the unpolishedstent 10 or alternative stent 30′ have planar parallel inner and outersurfaces 44′, 42′ and planar parallel leading and trailing surfaces 46′,48′ perpendicular to the surfaces 44′, 42′. The stent segments exhibitabrupt edges 50′, 52′, 54′, 56′ between adjacent surfaces 42′, 44′, 46′,48′. Roughness areas R are located on the surfaces 42′, 44′, 46′, 48′.After polishing, the stent segments 40 (FIG. 12) have greater surfacesmoothness and a cross-sectional contour which is more streamlined thanthe stent segment 40′. Specific details of the geometry and otherfeatures of the polished and streamlined stent 10 and its alternativesare incorporated by reference from U.S. patent application Ser. No.08/839,434, filed on Apr. 10, 1997, entitled “SURGICAL STENT HAVING ASTREAMLINED CONTOUR,” now U.S. Pat. No. 5,718,713.

In use and operation, when a stent 10 featuring stent segments 40 ofthis invention is implanted into a lumen L (FIGS. 16 and 18) with thestent segments 40 embedding slightly into the inner surface S of thelumen L and supporting the lumen L, blood/fluid flow B is only slightlydisrupted and restenosis and plaque buildup is minimized. When prior artstents are implanted (FIG. 17) stent segments 40 having more abruptcontours cause disruption in the blood/fluid flow B producing eddies Ewhich further disrupt blood/fluid flow B and encourage the formation ofplaque P, leading to restenosis, along the inner surface S at variouslocations along the inner surface S. Thrombus H is also stimulated byirregularities in surface finish exhibited by stent segments 40′ ofprior art stents.

With reference particularly to FIGS. 12 and 16, because the leadingcurves 60, 64 generally match the contour of the trailing curves 62, 66of each stent segment 40, the stent 10 featuring the stent segment 40can be reversed 180° with similar function in either orientation.Alternatively, should maximum streamlining of the stent segment 40 bedesired, the inner surface 44 can be provided with a more airfoil-likeasymmetrical contour which does not provide the leading surface 46 andtrailing surface 48 as mirror images of each other, but rather providesthe leading surface 46 with a smaller radius of curvature and thetrailing surface 48 with a larger radius of curvature or a taperinggradual slope, somewhat analogous to that of a tear drop incross-section. Such an asymmetrical surgical stent would necessarilyonly benefit from its form when implanted in a particular direction withregard to blood/fluid flow B through the lumen L.

Having thus described in detail the preferred contour and finishedsmoothness for the stent 10, it should be apparent that should differentfinished smoothness be desired, for various different purposes, variousdifferent curvatures and measurements of the contour of the stent 10could be similarly provided. This is particularly true when utilizingthe polishing method disclosed below. To accomplish polishing andstreamlining of the stent 10 to exhibit the contour discussed above, orany other desired contour, the following method is utilized with theapparatus discussed in detail below.

Before polishing the stent 10 according to the method of this invention,the stent 10 is preferably slightly modified to provide additionalsupport to the stent 10 during the polishing process. Specifically,cylindrical support ends 20 are attached to each end of the stent 10.Each cylindrical support end 20 is a cylindrical hollow substantiallyrigid construct preferably formed from the same material with which thecircumferential elements 12 and axial elements 14 of the stent 10 areformed. Each cylindrical support end 20 includes an outer edge 22 on anend of the cylindrical support end 20 most distant from the stent 10 andan inner edge 24 opposite the outer edge 22 and adjacent the stent 10.

A plurality of ties 25 extend from the inner edge 24 to the portions ofthe stent 10 adjacent to each cylindrical support end 20. The ties 25are preferably linear elongate segments of the stent 10 which areoriented in an axial direction (along arrow A of FIGS. 1 and 2) and arecolinear with axial elements 14 adjacent to the cylindrical support ends20. Preferably six ties 25 extend between the inner edge 24 and theportions of the stent 10 adjacent the cylindrical support ends 20. Eachtie 25 includes an outer end 26 adjacent the inner edge 24 and an innerend 28 opposite the outer end 26 and attached to the end of the stent 10adjacent the cylindrical support end 20.

The cylindrical support ends 20 can either be attached to the ends ofthe stent 10 before the polishing process or the cylindrical supportends 20 can be formed along with other portions of the stent 10originally so that the cylindrical support ends 20 are attached to thestent 10 at all times up until the polishing process is completed. Afterthe polishing process is completed, the cylindrical support ends 20 areremoved from ends of the stent 10 along with the ties 25, providing thestent 10′ (FIG. 18) in the desired configuration for implantation withina body lumen L.

The cylindrical support ends 20 are not radially expandable. Thus, thecylindrical support ends 20 help support the stent 10 during thepolishing process and prevent the stent 10 from being prematurelyradially expanded. Additionally, the cylindrical support ends 20 providea leading edge for the stent 10 during the polishing process and reducea risk that abrasive media M flowing along surfaces of the stent 10 willcause circumferential elements 12 at ends of the stent 10 to becollapsed or to otherwise collapse the stent 10 axially (along arrow Aof FIGS. 1 and 2) due to the added rigidity of the stent 10 when thecylindrical support ends 20 are attached thereto. Preferably, inner andouter diameters of the cylindrical support ends 20 match inner and outerdiameters of the stent 10.

With reference to FIG. 2, further details of the stent 10 with thecylindrical support ends 20 attached thereto are provided. Referencearrow C indicates a circumferential direction and reference arrows Rrepresent the radially direction in which the stent 10 is radiallyexpanded after removal of the cylindrical support ends 20 from the stent10. FIG. 2 shows the circumferential elements 12 in an undulatingfashion having not yet been radially expanded, as is the case while thecylindrical support ends 20 are attached thereto. In contrast, FIG. 1shows the circumferential elements 12 radially expanded to illustratethe difference in the configuration of the stent 10 after radialexpansion. The cylindrical support ends 20 would not be attached toother portions of the stent 10 when the stent 10 has been radiallyexpanded, along arrow R. Hence, FIG. 1 is a composite view which wouldnot actually exist, but depicts the configuration of the cylindricalsupport ends 20 in perspective and a perspective view of the radiallyexpandable surgical stent 10 after it has been radially expanded.

While various different systems could be utilized to effectively flowabrasive media past surfaces of the stent 10 for polishing, a preferredsystem for effectively flowing the fluid abrasive media M past surfacesof the stent 10, and particularly for polishing surfaces of the stent 10forming an inner diameter of the stent 10, are provided by the stentinterior polishing fixture 100 (FIGS. 3-6). The stent interior polishingfixture 100 is a rigid construct configured to provide a means to hold aseries of stents 10 motionless and provide conduits for fluid abrasivemedia M to flow adjacent surfaces of the stent 10 forming an innerdiameter of the stent 10. The interior polishing fixture 100 includes atop 102 parallel to and spaced from a bottom 104. Four parallel sides106 are oriented perpendicular to the top 102 and bottom 104. Hence, thetop 102, bottom 104 and sides 106 form an orthorhombic rigid mass ofsolid material.

A series of bores 108 pass from the top 102 through to the bottom 104 ofthe fixture 100. Preferably, each bore 108 is cylindrical in form andpasses along a line perpendicular to the top 102 and the bottom 104.Preferably, the bores 108 have a diameter which is similar to the innerdiameter of the stent 10. The fixture 100 is preferably not formed froma single unitary mass of material but rather from a series of rigidplates including two end plates 120 and a plurality of mid-plates 140sandwiched between the two end plates 120.

Each of the plates 120, 140 is securely held together with closure bolts112 passing through the interior polishing fixture 100 in an orientationparallel to the top 102 and bottom 104 of the fixture 100 andperpendicular to adjacent surfaces of the end plates 120. Preferably,two closure bolts 112 are provided passing through the fixture 100 atlocations which prevent the closure bolts 112 from intersecting with thebores 108. Each closure bolt 112 includes a head 114 on an end of eachbolt 112 opposite a threaded tip 116. Wing nuts 118 are provided whichthread onto the threaded tip 116. The closure bolts 112 can pass throughthe plates 120, 140 forming the fixture 100 with the head 114 of eachclosure bolt 112 adjacent one of the end plates 120 and the wing nuts118 threaded onto the closure bolts 112 adjacent the opposite end plate120. By tightening the wing nuts 118 against the end plate 120, theplates 120, 140 are securely sandwiched together without motion.

The bores 108 are aligned to pass between an end plate 120 and amid-plate 140 or between two adjacent mid-plates 140. In this way,access is provided to a cylindrical chamber 135 within the bore 108 whenthe plates 120, 140 of the interior polishing fixture 100 are separatedaway from each other. Preferably, three mid-plates 140 are providedbetween the two end plates 120 and five bores 108 are provided at eachtransition between an end plate 120 and an adjacent mid-plate 140 andbetween adjacent mid-plates 140, such that a total of twenty bores 108are provided passing from the top 102 to the bottom 104 of the interiorpolishing fixture 100.

With particular reference to FIG. 5, specific details of each end plate120 are provided. Each end plate 120 is a unitary rigid mass of materialwhich forms a portion of the interior polishing fixture 100. Each endplate 120 includes an outer surface 122 which does not include anyportion of a bore 108 thereon. Each end plate 120 includes a bottom 124parallel to and spaced from a top 128 which form portions of the top 102and bottom 104 of the interior polishing fixture 100. Each end plate 120also includes lateral sides 126 parallel to each other and orientedperpendicular to the bottom 124 and top 128.

An inner surface 130 is provided on the side of the end plate 120opposite the outer surface 122. This inner surface 130 is similarlyformed on each of the two end plates 120. The inner surface 130 iscontoured to include portions of the bores 108 therein. Each innersurface 130 includes a flat plane 132 defining portions of the innersurface 130 which do not include portions of the bores 108 therein. Twobolt holes 133 pass through the inner surface 130 and entirely throughto the outer surface 122 of each end plate 120. The bolt holes 133 havea diameter which accommodates passage of the closure bolts 112 therethrough. The bolt holes 133 are preferably located at a positionintermediate between the bottom 124 and top 128 of the end plate 120 andbetween a lateral side 126 of the end plate 120 and a closest bore 108.Alternatively, the bolt holes 133 can be located at any location on theinner surface 130 where the flat plane 132 is provided, rather than aportion of a bore 108.

Each bore 108 includes a void defined by a cylindrical chamber 135therein. The cylindrical chamber 135 is formed by having a cylindricalchamber wall 134 contoured into the inner surface 130 of each end plate120. Preferably, with five bores 108 passing between each end plate 120and an adjacent mid-plate 140, five cylindrical chamber walls 134 areformed in the inner surface 130. The cylindrical chamber wall 134 issemicylindrical in form providing exactly one-half of the cylindricalchamber 135. The cylindrical chamber wall 134 does not extend all theway up to the top 128 or to the bottom 124 of the end plate 120. Rather,the cylindrical chamber wall 134 forms an interior detail of one of thebores 108 which does not extend to the top 102 and bottom 104 of theinterior polishing fixture 100.

The cylindrical chamber wall 134 preferably has a diameter similar to anouter diameter of the stent 10. The cylindrical chamber wall 134 extendsfrom a top chamber end 136 to a bottom chamber end 137 (FIG. 4). Abovethe top chamber end 136 a top cylindrical bore wall 138 (FIG. 5) isprovided forming a portion of the bore 108 extending from thecylindrical chamber 135 up to the top 102 of the fixture 100. A bottomcylindrical bore wall 139 (FIG. 5) similarly extends from the bottomchamber end 137 to the bottom 104 of the interior polishing fixture 100.

The top cylindrical bore wall 138 and bottom cylindrical bore wall 139form exactly half of the cylindrical bore 108 leading into and out ofthe cylindrical chamber 135. The top chamber end 136 and bottom chamberend 137 provide a transition between the larger diameter of thecylindrical chamber 135 and the smaller diameter of the bores 108. Withthe top chamber end 136 and bottom chamber end 137 spaced apart similarto an axial length of the stent 10, a stent 10 can be located within thecylindrical chamber 135 with the outer diameter of the stent 10 adjacentthe cylindrical chamber wall 134 and with the cylindrical support ends20 of the stent 10 adjacent the top chamber end 136 and bottom chamberend 137. In this position, the inner diameter of the stent 10 is alignedwith the bore walls 138, 139 forming the bores 108.

The mid-plates 140 are similar to the end plates 120 except that eachmid-plate 140 includes two contoured surfaces 142 each similar incontour to the contour provided by the inner surface 130 of each endplate 120. The mid-plates 140 include a bottom 144 parallel to andspaced from a top 148 with two parallel lateral sides 146 orientedperpendicular to the bottom 144 and top 148.

With particular reference to FIG. 6, other portions of the stentpolishing apparatus which attach to the interior polishing fixture 100are described in detail. A hose 150 is located adjacent the top 102 ofthe interior polishing fixture 100. The hose 150 provides a source forfluid abrasive media M which can lead from a reservoir up to the top 102of the fixture 100. A lower end 151 of the hose 150 is located adjacenta manifold plate 152. The manifold plate 152 is a rigid construct whichis configured to seal against the top 102 of the fixture 100 with amanifold chamber 153 therein provided in fluid communication with eachof the bores 108 in the interior polishing fixture 100. The. manifoldchamber 153 is also open to the interior of the hose 150 so that fluidabrasive media M can flow through the hose 150, out of the lower end 151of the hose 150 and into the manifold chamber 153; where it can thenflow into each of the bores 108 in the interior polishing fixture 100.

A top clamp plate 154 is located over the manifold plate 152 and securesthe manifold plate 152 to the top 102 of the fixture 100. A hose opening155 is located in the top clamp plate 154 so that the hose 150 can stillaccess the manifold chamber 153. A bottom clamp plate 156 is locatedadjacent the bottom 104 of the fixture 100. The bottom clamp plate 156includes a central opening 157 which leaves the bores 108 in the bottom104 unblocked. A series of clamp bolts 158 with wing nuts 159 passthrough the top clamp plate 154 and bottom clamp plate 156 and can bethreaded together, drawing the bottom clamp plate 156 and top clampplate 154 toward each other and securing the manifold plate 152 and hose150 adjacent the top 102 of the interior polishing fixture 100.

In use and operation, the interior polishing fixture 100 is utilized topolish surfaces forming an inner diameter of the stent 10 in thefollowing manner. Initially, the closure bolts 112 are removed from thefixture 100 and the end plates 120 and mid-plates 140 are each separatedfrom each other. Each cylindrical chamber 135 is then preferablyprovided with a separate stent 10 and the end plates 120 and mid-plates140 are placed adjacent each other with the closure bolts 112 in placesecuring the plates 120, 140 together. The manifold plate 152 is thenplaced over the top 102 of the fixture 100 with the hose 150 interfacingwith the manifold plate 152. The top clamp plate 154 and bottom clampplate 156 are then oriented over the top 102 and bottom 104,respectively, of the fixture 100 and the wing nuts 159 are tightened tosecure the manifold plate 152 and hose 150 in position adjacent the top102 of the fixture 100.

Fluid abrasive media M is then passed (along arrow F) through the hose150 into the manifold chamber 153, through the bores 108 and into thecylindrical chamber 135 where the fluid abrasive media M flows adjacentsurfaces forming the inner diameter of the stent 10. The media M thenflows out of the bores 108 and through the central outflow opening 157in the bottom clamp plate 156 (along arrow D).

Preferably, the fluid abrasive media M flows through the fixture 100 andpast the inner diameter of the stent 10 for a desired amount of time andthen the fluid abrasive media M is caused to flow in a reverse directionagainst the inner diameter of the stent 10. Reversal of flow of theabrasive media M can be accomplished by removing the fixture 100 fromthe clamp plates 154, 156, reversing the fixture 100 and replacing thefixture 100 within the clamp plates 154, 156 with the top clamp plate154 and manifold plate 152 adjacent the bottom 104 of the fixture 100.Alternatively, the hose 150 and a source of fluid abrasive media M canbe configured to allow flow in both directions through the bores 108 ofthe fixture 100.

If a streamlined contour is desired for surfaces forming the innerdiameter of segments 40 (FIG. 12) forming the stent 10, rather than merepolishing of surfaces of the stent 10, the fluid abrasive media M wouldbe allowed to flow through the fixture 100 for a greater amount of timeor the fluid abrasive media M could be provided with particles having agreater amount of abrasiveness. If a streamlined contour of symmetricalform is desired, the amount of time with which the media M flows in afirst direction should approximate the amount that it flows in a reversedirection.

Polishing of surfaces of the stent 10 can be further enhanced byultrasonically vibrating the abrasive media M as the abrasive media Mflows through the fixture 100 and adjacent surfaces of the stent 10.Specifically, the hose 150 and a source of fluid abrasive media M on anend of the hose 150 opposite the lower end 151 can be fitted with anultrasonic vibration generation device which causes high frequencyagitation of the fluid abrasive media M as it flows through the fixture100. Another parameter which can be utilized to enhance theeffectiveness of the fluid abrasive media M is to supply the fluidabrasive media M at a pressure greater than atmospheric pressure as thefluid abrasive media M passes through the fixture 100. Such enhancedpressure can be provided with pistons in communication with the fluidabrasive media M or other pumps or other pressure generation meansacting on the fluid abrasive media M before or during fluid abrasivemedia M flow through the hose 150 and into the fixture 100.

The fluid abrasive media M can either exit the bores 108 of the fixture100 into an atmospheric pressure region without any specific enclosuresor it can be fitted with an outlet hose similar to the hose 150 forcollection of the fluid abrasive media M. If desired, the fluid abrasivemedia can oscillate back and forth through the bores 108 rather thanflowing continuously in a first direction through the bores 108 and thenbeing reversed in direction to flow in an opposite direction through thebores 108.

The sizing of the bores 108 to have a similar diameter to the innerdiameter of the stent 10 and the chamber 135 to have a similar diameterto the outer diameter of the stent 10 prevents the fluid abrasive mediaM from flowing past surfaces forming the outer diameter of the stent 10and maintains surfaces of the stent 10 forming the outer diameter in asubstantially unpolished and unstreamlined form. It has been found to beparticularly advantageous that the inner diameter of the stent 10 bepolished and streamlined such that blood B or body fluids can passthrough a lumen L where the stent 10 is located and radially expanded ina manner which decreases turbulence of blood B flowing through the lumenL (FIGS. 16 and 17).

An alternative stent segment 90 is shown in FIG. 13 where only the innerdiameter of the stent segment 90 has been polished and streamlined. Anouter surface 92 remains substantially planar with outer edges 96abruptly transitioning to the inner edges 98 leading to the innersurface 94 which has been streamlined. Areas of roughness R can eitherremain on the outer surface 92 where the stent segment 90 is locatedadjacent an inner surface S of the lumen L (FIGS. 16 and 17) or bepolished merely to remove roughness R but not to streamline or round offedges of the stent segment 90. Such an alternative stent segment 90would typically result in utilization of the stent interior polishingfixture 100 alone, with little or no utilization of the stent exteriorpolishing fixture 200 described below.

While various different parameters can be selected in performing thepolishing process disclosed herein, it has been found effective andpreferable to have abrasive media particle sizes between 0.008 and0.0003 inches. It has been found preferable to maintain an elevatedpressure between 300 and 800 pounds per square inch. An abrasive media Mwhich has been found to be effective is aluminum oxide or siliconcarbide. Alternatively, diamond particles could be utilized.

More specifically, successful tests were run of a fixture 100 similar tothat disclosed herein utilizing aluminum oxide with a particle size of0.0007 inches at a pressure of 500 pounds per square inch with a totalprocess time of thirteen minutes (7.5 minutes each direction) and adesirable surface finish with streamlining of stainless steel stentsegments 40 similar to that shown in FIGS. 12 and 15 resulted. Inanother test, silicon carbide was utilized with a particle size of 0.006inches at 500 pounds per square inch with a total process time ofthirteen minutes and similar contours to those shown in FIGS. 12 and 15resulted. Specifically, surface roughness R was reduced to eliminationof any prominences greater than 5 micro inches above adjacent portionsof the surfaces.

Once the stents 10 have been polished by flow of the fluid abrasivemedia M through the fixture 100, the hose 150 and other apparatusadjacent the fixture 100 are removed and the individual plates 120, 140are separated from each other for removal of the stents 10 therefrom.The cylindrical end supports 20 are then removed from the stents 10,providing a polished stent 10′ (FIG. 18) which is now ready forimplantation and radial expansion within a body lumen L as is known inthe art.

With particular reference to FIGS. 7-9, details of the stent exteriorpolishing fixture 200, which is configured to particularly providepolishing for surfaces forming an outer diameter of the stent 10, aredescribed in detail. The stent exterior polishing fixture 200 is shownin FIGS. 7-9 as having a void therein for supporting only a single stent10 for polishing therein. However, the exterior polishing fixture 200could be modified to include multiple separate voids and multipleseparate plates as in the case of the interior polishing fixture 100such that multiple stents 10 can be polished simultaneously within thestent exterior polishing fixture 200. For convenience, the details ofthe stent exterior polishing fixture 200 will be described for anembodiment where only a single void for a single stent 10 is providedwithin the stent exterior polishing fixture 200.

The exterior polishing fixture 200 is a solid rigid mass of materialhaving a top 202 parallel to and spaced from a bottom 204 with sides 206extending perpendicularly between the top 202 and the bottom 204.Multiple slanted bores 208 pass through the top 202 and bottom 204 andcommunicate together such that fluid abrasive media M can flow entirelythrough the fixture 200 from the top 202 to the bottom 204, in a mannersimilar to that described above with respect to the interior polishingfixture 100.

The exterior polishing fixture 200 is formed from two identical endplates 210 having an outer surface 212 extending perpendicularly betweena bottom 214 and a top 218 which form portions of the bottom 204 and top202, respectively, of the exterior polishing fixture 200. A lateralsurface 216 defines surfaces of the end plate 210 perpendicular to thebottom 214 and top 218 and also perpendicular to the outer surface 212.

A cylindrical recess 220 somewhat analogous to the cylindrical chamber135 in the interior polishing fixture 100 is located within the exteriorpolishing fixture 200 in fluid communication with the slanted bores 208.The cylindrical recess 220 is formed between the two end plates 210 suchthat the cylindrical recess 220 is in fact formed in an inner surface230 parallel to and spaced from the outer surfaces 212 of the two endplates 210. Each inner surface 230 includes a flat plane 232 definingportions of the inner surface 230 where the cylindrical recess 220 isnot located and a cylindrical recess wall 234 defining exactly one-halfof the cylindrical recess 220. The cylindrical recess wall 234 ispreferably semi-cylindrical in form and has a diameter greater than anouter diameter of the stent 10.

A top blind bore 240 extends up from the cylindrical recess 220 betweenthe multiple slanted bores 208. The top blind bore 240 extends up to atop bore wall 242 perpendicular to the cylindrical recess wall 234 ofthe cylindrical recess 220. A bottom blind bore 250 similar to the topblind bore 240 but below the bottom of the cylindrical recess 220 isalso located within the exterior polishing fixture 200. The bottom blindbore 250 includes a bottom bore wall 252 parallel to the top bore wall242.

Between the top bore wall 242 and bottom bore wall 252 and thecylindrical recess wall 234 two similar collar support regions 260 arelocated. The top blind bore 240, bottom blind bore 250 and two collarsupport regions 260 are each cylindrical in form but exhibit differentdiameters extending away from a central axis common with the cylindricalrecess 220. A recess edge 262 defines a diameter transition between thecylindrical recess wall 234 and the two collar support regions 260. Abore edge 264 is located at a transition between the collar supportregions 260 and the two blind bores 240, 250.

Preferably, the slanted bores 208 extend from the top 202 and the bottom204 up into the collar support regions 260. Preferably, two slantedbores 208 are located within each end plate 210 such that a total offour slanted bores 208 pass from the top 202 into the cylindrical recess220 and four slanted bores 208 pass from the bottom 204 into thecylindrical recess 220.

The cylindrical recess wall 234 has a diameter greater than an outerdiameter of the stent 10. The collar support regions 260 have a diametersimilar to an outer diameter of the stent 10. The blind bores 240, 250have a diameter similar to an inner diameter of the stent 10.

A shaft 270 is provided having a length similar to a distance betweenthe top bore wall 242 and the bottom bore wall 252 and having a diametersimilar to a diameter of the blind bores 240, 250 and the inner diameterof the stent 10. Thus, the stent 10 can be placed on the shaft 270 withthe inner diameter of the stent 10 adjacent the shaft 270. The shaft 270includes a top end 272 parallel to and spaced from a bottom end 274 witha cylindrical surface 276 sized to be located adjacent the innerdiameter of the stent 10. The shaft 270 is located within the exteriorpolishing fixture 200 with the top end 272 within the top blind bore 240and the bottom end 274 within the bottom blind bore 250 when theexterior polishing fixture 200 is in use for polishing exterior surfacesof the stent 10.

An upper collar 280 is provided having an inner surface 282 with adiameter similar to a diameter of the cylindrical surface 276 of theshaft 270. The upper collar 280 includes an outer surface 284 with adiameter similar to a diameter of the collar support regions 260 and theouter diameter of the stent 10. The upper collar 280 is a hollowcylindrical rigid construct extending from a circular top edge 286 to acircular bottom edge 288. The upper collar 288 has a length between thetop edge 286 and the bottom edge 288 which causes the upper collar 280to be longer than a distance within each collar support region 260 fromthe recess edge 262 to the bore edge 264. Thus, when the upper collar280 is located on the shaft 270 within the fixture 200 the upper collar280 extends down into the cylindrical recess 220 somewhat. A lowercollar 290 is provided with a form similar to that of the upper collar280.

Preferably, the cylindrical recess 220 has a length between the recessedges 262 which is slightly greater than a length of the stent 10 andactually includes a length of the stent 10 and a length of portions ofeach collar 280, 290 which extend from the recess edges 262 into thecylindrical recess 220. Thus, when the shaft 270 is located within theexterior polishing fixture 200 with the top end 272 within the top blindbore 240 and the bottom end 274 within the bottom blind bore 250 andwith the collars 280, 290 located upon the shaft 270 and within thecollar support regions 260 (as shown in FIG. 7), sufficient space isprovided between the upper collar 280 and the lower collar 290 for thestent 10 to be placed over the shaft 270 and between the upper collar280 and the lower collar 290 without any axial motion of the stent 10between the collars 280, 290 within the exterior polishing fixture 200allowed.

Preferably, the shaft 270, upper collar 280 and lower collar 290 areeach separate pieces so that the stent 10 can be easily placed upon theshaft 270 with the collars 280, 290 also on the shaft 270 adjacent endsof the stent 10. The shaft 270, collars 280, 290 and stent 10 can thenbe simultaneously placed together within the cylindrical recess 220, topblind bore 240, bottom blind bore 250 and collar support regions 260 asthe two end plates 210 of the exterior polishing fixture 200 are closedtogether.

Preferably, closure bolts similar to the closure bolts 212 of theinterior polishing fixture 100 are utilized to secure the end plates 210together. Also, a clamping system, manifold plate and hose are providedin a manner similar to that discussed above with respect to the interiorpolishing fixture 100 to deliver fluid abrasive media M through theslanted bores 208 and into the cylindrical recess 220.

Because the cylindrical recess 220 has a diameter greater than the outerdiameter of the stent 10, and because the shaft 270 prevents fluidabrasive media M from flowing adjacent interior surfaces of the stent10, the fluid abrasive media M is caused to flow exclusively oversurfaces of the stent 10 forming the outer diameter of the stent 10. Aswith the use of the interior polishing fixture 100 discussed above,various different fluid abrasive media M can be utilized with differentpressures, durations, particle sizes, and ultrasonic vibration, asrequired to produce a desired finished surface for outer surfaces of thestent 10. Preferably, the outer diameter of the stent 10 is polished tohave a smooth surface but is not significantly streamlined. Rather thestent segments 40 are provided with relatively abrupt leading andtrailing edges 50, 52 (FIGS. 12 and 15) so that the stent 10 will remainsecurely in place when radially expanded within a body lumen L, withoutsliding along the inner surface S of the body lumen L, but preferablydoes not have patches of roughness R (FIGS. 13 and 14) which might causeirritation of the body lumen L and lead to thrombus, restenosis or otherdetrimental complications.

Preferably, the slanted bores 208 enter into the cylindrical recess 220at a location where the upper collar 280 and lower collar 290 areprovided. Thus, extreme upper portions of the cylindrical recess 220provide a zone where the fluid abrasive media M can flow laterallybetween adjacent slanted bores 208 and fill the cylindrical recess 220before the fluid abrasive media M flows down to the cylindrical recess220 and comes into contact with surfaces of the stent 10 forming theouter diameter of the stent 10. In this way, all locations within thecylindrical recess 220 are provided with fluid abrasive media M forpolishing, without any vacant regions in the abrasive media M flow.

While the exterior polishing fixture 200 has been separately disclosedand described with respect to a preferred interior polishing fixture100, it is understood that a fixture could be provided which allowsabrasive media M to flow simultaneously adjacent an inner diameter andan outer diameter of the stent 10 such that a single composite fixturerather than two separate fixtures would be provided. The benefits ofsuch a composite fixture, including overall simplification of the stentpolishing process would necessarily be compared with the addedcomplexity of such a fixture and difficulties associated with securingthe stent 10 in position within such a fixture and adequately supportingthe stent 10 such that the stent 10 is not damaged during high pressureflow of the abrasive media M adjacent surfaces of the stent 10.

Other further modifications to the fixtures 100, 200 and the polishingprocess could also be resorted to without departing from the scope ofthe invention. The specific embodiments disclosed herein are providedmerely by way of example and to provide a best mode and preferredembodiment for practicing this invention and should not be considered asfurther limiting the claims included herein below.

What is claimed is:
 1. A method for polishing surfaces of a cylindricalradially expandable surgical stent including the steps of: selecting anabrasiveness for particles within a fluid abrasive media; providing asource of the fluid abrasive media; orienting the radially expandablesurgical stent with a central axis thereof extending in an axialdirection; subjecting the fluid abrasive media to elevated pressuresubstantially between 300 and 800 p.s.i.; and flowing the abrasive mediapast the radially expandable surgical stent in an axial direction withthe abrasive media coming into physical contact with the surface of theradially expandable surgical stent, wherein the step of flowing includesmaintaining the flowing past an inner stent surface for a length of timesufficient to abrade the edges of the inner stent surface until saidedges are streamlined in shape, and maintaining the flowing past anouter stent surface for a length of time sufficient only to polish theouter stent surface.
 2. A method for polishing surfaces of a cylindricalradially expandable surgical stent including the steps of: selecting anabrasiveness for particles within a fluid abrasive media; providing asource of the fluid abrasive media; orienting the radially expandablesurgical stent with a central axis thereof extending in an axialdirection; subjecting the fluid abrasive media to elevated pressuresubstantially between 300 and 800 p.s.i.; and flowing the abrasive mediapast the radially expandable surgical stent in an axial direction withthe abrasive media coming into physical contact with the surface of theradially expandable surgical stent, wherein the step of flowing includesmaintaining the flowing for a length of time sufficient to abrade theedges of an inner stent surface until said edges have a greater radii ofcurvature than radii of curvature of outer edges bordering an outersurface of the stent.
 3. A method for polishing surfaces of acylindrical radially expandable surgical stent having a central axis,comprising: providing a source of the fluid abrasive media; flowing theabrasive media past the stent in an axial direction with the abrasivemedia coming into physical contact with the surfaces of the stent; andmaintaining the flowing past an inner stent surface for a length of timesufficient to abrade the edges of the inner stent surface until saidedges are streamlined in shape, wherein the flowing of the abrasivemedia past an outer stent surface is maintained for a length of timesufficient only to polish the outer stent surface.
 4. A method forpolishing surfaces of a cylindrical radially expandable surgical stenthaving a central axis, comprising: providing a source of the fluidabrasive media; flowing the abrasive media past the stent in an axialdirection with the abrasive media coming into physical contact with thesurfaces of the stent; and maintaining the flowing past an inner stentsurface for a length of time sufficient to abrade the edges of the innerstent surface until said edges are streamlined in shape, wherein thestep of flowing includes maintaining the flowing for a length of timesufficient to abrade the edges of an inner stent surface until saidedges have a greater radii of curvature than radii of curvature of outeredges bordering an outer surface of the stent.
 5. A method for polishingsurfaces of a cylindrical radially expandable surgical stent having acentral axis, comprising: providing a fluid abrasive media containingparticles having a size substantially between 0.0003 and 0.008 inches;providing a source of the fluid abrasive media; maintaining the fluidabrasive media at an elevated pressure substantially between 300 and 800p.s.i.; flowing the abrasive media past the stent in an axial directionwith the abrasive media coming into physical contact with the surfacesof the stent; maintaining the flowing past an inner stent surface for alength of time sufficient to abrade the edges of the inner stent surfaceuntil said edges are streamlined in shape; and maintaining the flowingpast an outer stent surface for a length of time sufficient to polishthe outer stent surface.